Gardeners agree that it takes a lot of work to keep rose bushes beautiful and healthy. Despite your best efforts, a plethora of insect pests are willing and eager to chow down on your rose bush and destroy your hard work. Being able to identify and stop these insects goes a long way in catching an infestation early, before it gets out of hand.
Japanese beetles (Popillia japonica) are exotic insects of the scarab beetle category. These pests are dark green and tan, measuring about 1/2 inch long. Japanese beetles are characterized by five patches of white hair along the underside of their abdomen. The false Japanese beetle (Strigoderma arbicola), is similar in size and appearance, but does not possess these white patches.
Adult specimens of both the Japanese beetle and false Japanese beetle eat the foliage and flowers of rosebushes. Larvae of these insects prefer the roots of rose plants. Japanese and false Japanese beetles do not feed exclusively on roses and will defoliate most flowering plants.
If there are only a few Japanese or false Japanese beetles, plucking them from your rose bushes is an acceptable method of removal. In the event that an infestation has gotten out of hand, insecticides may be necessary.
There are over 400 types of aphids in the world, but Macrosiphum rosa, the Rose Aphid, prefers rose bushes. Rose aphids suck fluids from shoots, buds and leaves, dining on the rich nitrogen in these areas. In addition to defoliating rose bushes, aphids leave a sweet, sticky substance wherever they travel. This substance, termed "honeydew," attracts other garden pests such as ants and sawflies. One batch of aphid eggs can yield thousands of aphids throughout the season, making these pests hard to eradicate and devastating if left to their own devices.
There are a variety of ways to remove or control an aphid infestation. Hand removal is a possibility, as are pesticides. Due to their ability to reproduce in prolific numbers, many gardeners are turning to non-chemical removal techniques, such as high-powered water spraying, and utilizing the natural predators of aphids, notably ladybugs.
The larvae of carpenter bees, Ceratina spp, are given the descriptive name of "cane borers." These insects drill holes, or "bore", into the tops of newly pruned rose stems. They lay eggs on the top of these canes in late spring and early summer.
When the eggs hatch, the cane borers work their way down the stem of the plant. The only way to remove cane borers is to prune the stems that house them. As the cane borer works its way down the rose bush, the stem withers and dies. If a cane borer reaches the base of the plant, called the "bud union," there is a good chance the rose bush will die.